The present invention relates generally to matrix amplifiers and more particularly to hybrid matrix amplifiers employing a unique combination of magnetic field and electric field controlled amplifiers.
Since the development of distributed amplifiers by Percival in British Patent 460,562, a variety of solid state circuitry schemas have recently been developed to implement this concept. Most notably, recent distributed amplifiers as described by Schindler et al in "A K/Ka-Band Distributed Power Amplifier with Capacitance Drain Coupling", IEEE Transactions on Microwave Theory and Techniques Vol. 36, No. 12, pp. 1902-1907 (1988) and Niclas et al in "The Matrix Amplifier: A High-Gain Module for Multi-octave Frequency Bands", IEEE Transactions MTT-35, No. 3, pp. 296-306 (1987) have both employed field effect transistors (FETs) as the active devices to achieve signal gain or amplification. The attractiveness of such distributed amplifiers resides in their ability to achieve moderate gain at high frequencies (e.g. GHz) over wide bandwidths (e.g. 10-30 GHz). Use of such distributed amplifiers for signal processing and communications applications can also require high efficiencies, low Noise Figures and reasonably high output power. However, present distributed amplifiers cannot maintain low Noise Figures, large bandwidth and high output power requirements simultaneously.
Amplification of a signal with two or more active devices can be classified as multiplicative or additive. In the former case, the overall gain is proportional to the product of the gains of each active device, while in the latter case, gain is proportional to the sum of the gains from each active device. The vast majority of amplifiers make use of the multiplicative process. The most notable exception is the distributed amplifier, described above, whose amplifying mechanism is based on the additive concept. While amplifiers which employ the multiplicative concept can yield greater gain, they tend to be band width limited as well as noisier.
More recently, Niclas et al described (N.times.M) matrix amplifiers which combined active devices employing both the multiplicative and additive concepts in a single circuit. Its purpose was to enhance the characteristics features of both devices (i.e. increase the gain of additive devices and increase the bandwidth of multiplicative devices). Niclas' circuit consisted of an array of N rows of distributed amplifiers and M columns or stages of cascaded active devices in each distributed amplifier wherein each active device in a row is further linked to a corresponding active device in adjacent rows of distributed amplifiers. The active devices of Niclas' circuit are all FETs.
In spite of such advances, a need still exists for matrix amplifiers having a low Noise Figure for amplifying signals of very low amplitude (e.g. of the order of .mu.A or mV) which cannot be adequately satisfied by existing matrix amplifiers. In particular, each row of distributed amplifiers in existing matrix amplifiers is limited to no more than .about.6-10 cascaded FET devices because the gate resistance of the FETs can cause the input signal to be greatly attenuated. The present invention is not limited in the number of active devices which can be employed in each row of cascaded devices in the distribute amplifier. Consequently, the present invention can have greater gain. Moreover, since the matrix amplifier of the present invention includes superconducting active devices having very low Noise Factors, it is capable of processing very low amplitude signals as well as yielding a much broader bandwidth (e.g. &gt;50 GHz).